The present invention relates to improvements in power trains for use in motor vehicles and to improvements in methods of operating clutches and transmissions in such power trains.
Automation of heretofore manually performed gear selecting, gear shifting and clutch engaging/disengaging operations is gaining in importance and popularity by the operators of motor vehicles. An advantage of automated power trains which do not employ a torque converter is their lower cost, a higher efficiency and the resulting reduction of fuel consumption.
A drawback of presently known power trains with automated torque transmitting systems (such as friction clutches) and automated change-speed transmissions is that they must employ more than two actuators (such as electric or hydraulic motors), namely a first actuator which serves to select the condition of an engageable and disengageable clutch normally operating between the prime mover and the transmission of the power train (the clutch must be disengaged during shifting of the transmission into a selected gear); a second actuator which operates the gear selecting means of the transmission (such gear selecting means serves to select one of several paths for movements of a device which actually shifts the transmission into and out of a selected gear); and a third actuator for the gear shifting device. A transmission wherein the selection of gears and the shifting into and from selected gears involve the utilization of two discrete actuators can comprise a shaft which is movable axially by a first actuator to thus select one of a plurality of different gears and which is turnable by a second actuator to thus shift the transmission into or from a selected gear. It is also possible to reverse the functions of the first and second actuators, i.e., the first actuator can move the shaft axially to shift the transmission into and from a selected gear, and the second actuator can turn the shaft in order to select any one of a plurality of different gears.
Each of the three actuators must receive signals from at least one control circuit to operate in accordance with a predetermined program. Such control circuits (each of which can employ or cooperate with several sensors) contribute to the bulk and cost of the power train and render the power train prone to malfunctioning.